Battery-Electric Ships: Economics, Limits and Prospects

Battery-electric propulsion is already the least-cost zero-emission option on short, high-utilisation routes, and is displacing incumbents among ferries, harbour craft and inland vessels. This chapter argues that its economics turn less on energy density than on the opportunity cost of stored energy: batteries must be cycled frequently to pay, so the binding constraint on longer routes is the inability to recharge at sea. Because shipping is a technology taker that inherits cheaper, safer, longer-lived cells from far larger road-transport and grid-storage markets, the economically electrifiable boundary moves outward with global cell production, largely independent of maritime demand-whereas synthetic marine fuels must finance their own scale-up. Comparing shipping with road freight isolates six differences: fuel price, energy efficiency and safety disadvantage maritime electrification, while lower sensitivity to battery weight and large electrical auxiliary loads on cruise and container ships favour it. We trace how powertrain architecture - from mechanical drive with power take-in to fuel-electric and pure-electric - and onboard DC distribution shape adoption, and add an often-overlooked energy-security dividend: electrification converts a disruptible fuel import into a one-off equipment purchase followed by domestic energy. Electrification advances along a predictable ladder, from harbour ferries through inland and short-sea vessels to port-anchored coastal routes, with deep-sea trades reachable only through infrastructure-mediated configurations, if at all. Low-regret policy levers include port electricity infrastructure, harmonised standards and broad emissions pricing.